Theoretical study of the aza-Wittig reaction X3P=NH+O=CHCOOH→X3P=O+HN=CHCOOH for X=Cl, H and CH3

The title aza-Wittig reaction has been studied theoretically by means of ab initio calculations. Geometries were optimized at the HF/6-31G∗∗ level, and single-point energy calculations were performed at the MP2/6-31G∗∗ level using the HF/6-31G∗∗ structures. Calculated results show that two transition states exist on the aza-Wittig reaction surface and that both the first and second forward barriers decrease in the order Cl>H>CH3. It can be seen that the substituent effect makes the aza-Wittig reaction for X=CH3 and H more favorable than for X=Cl.